1. Field of the Invention
The present invention generally relates to a method for forming an armrest of the type rotatably attached to a lateral side of a seat back of an automotive seat. In particular, the invention is directed to a method involving a foaming step, which is suited for forming an armrest of this type provided with a rotation device for allowing the armrest to be rotatable vertically and laterally at the seat back.
2. Description of Prior Art
Among armrests for use with an automotive seat, known is a rotatable type of armrest which is rotatably attached to a lateral side of a seat back of the seat, so that the armrest can be rotated between a horizontally extending use position and an upright non-use position. In the horizontally extending use position, the armrest extends horizontally from the seat back to support a passenger""s arm, and in the upright non-use position, the armrest is stored upright on and along the vertical side wall of the seat back. Also, as disclosed from the Japanese Patent Laid-Open Publication No. 2001-61595 for instance, there is such a type of armrest that is provided with a rotation device for allowing the armrest body to be rotatable in vertical and lateral directions. In this prior art, the armrest body is of a known armrest configuration having a cut-out corner area in which a rotatable part of the rotation device is exposed, and that particular rotatable part is connected with a lateral wall of a backrest or seat back of automotive seat. The rotatable part of rotation device comprises a connecting bracket pivotally connected with the seat back lateral wall and a rotatable shaft unit rotatably connected with an armrest frame provided in the armrest body. Thus, the armrest body may not only be rotated vertically via the connecting bracket, but also be rotated laterally (i.e. in either leftwards or rightwards) via the rotatable shaft unit, with respect to the seat back (see FIG. 7 for instance).
In forming this particular sort of armrest, the armrest frame and a part of the rotation device are first placed in a preformed three-dimensional trim cover assembly to provide an initially assembled armrest. Then, such initially assembled armrest is set in a foaming die device, followed by injecting a liquid foaming material in the interior of the trim cover assembly. The liquid foaming material is cured and expanded in the trim cover assembly, so that a foam padding is created and filled therein together integrally with the armrest frame and rotation device, excepting the above-stated connecting bracket. Normally, the foaming die device used is of a hinged type wherein a movable upper die is pivotally connected via a hinge to a lower stationary die. Thus, an operator flips over the upper die from the lower die via the hinge to open the two dies in order that he or she will place the initially assembled armrest in the dies before foaming operation. Also, after the foaming operation, the operator flips over the upper die from the lower die via the hinge to take out the foamed resultant armrest therefrom.
However, in the foregoing type of armrest, the rotatable part of rotation device is formed from a hard metallic material and projects outwardly from the armrest body. This projected hard part of armrest has been found defective in interfering with the foregoing hingedly opening and closing of the upper die with respect to the lower die, which makes it entirely difficult or impossible to place and take out an armrest unit from the two dies. Furthermore, that rotatable part of rotation device is free to rotate in all angles and therefore can not be precisely located and retained at a given position within the dies.
In view of the above-stated drawbacks, it is therefore a primary purpose of the present invention to provide an improved method which makes it easy to form a rotatable armrest with rotation device under optimal conditions, using a hinged foaming die device.
To achieve such purpose, in accordance with the present invention, there is basically provided a method comprising the steps of;
providing an incomplete armrest unit pre-assembled by: a trim cover assembly of three-dimensional configuration formed in a shape conforming to an outer shape of armrest; and a rotation means attached to the trim cover assembly;
providing a hinged foaming die means comprising a stationary die and a movable die rotatably connected via a hinge means with the stationary die;
providing a core die means to be accommodated between the stationary and movable dies so as to cover and retain the rotation means of the incomplete armrest unit therebetween;
providing a location pin adapted to locate and retain the rotation means at a predetermined point in the stationary die;
placing the incomplete armrest unit in the stationary die;
retaining the rotation means of the incomplete armrest unit at the predetermined point in the stationary die by means of the location pin;
setting the core die means on the stationary die so as to cover and support the rotation means of incomplete armrest unit;
causing the movable die to rotate about the hinge means toward said stationary die, thereby closing both movable and stationary dies;
then, injecting a liquid foaming material into inside of the trim cover assembly; and
subjecting the incomplete armrest unit to foaming by curing the liquid foaming material into a foam padding filled in the trim cover assembly, whereby the armrest of rotatable type with the rotation means is formed.
Accordingly, due to the combination of the core die piece and location pin, the rotation means, which is prone to undesired movement and rotation, can be easily and precisely located at a given point within stationary and movable dies and retained therein against any movement and rotation. Hence, a resultant armrest can be easily formed in a predetermined shape, and also, it is easy to open the movable die from the stationary die to take out the resultant armrest therefrom.
Preferably, the core die piece may have a curved upper surface, whereas the movable die may have, formed therein, a curved recessed area having a curvature substantially equal to a curvature of the curved upper surface of core die piece, whereby the movable die is rotatable relative to the hinge means, without interference with the core die piece, in a direction toward and away from the stationary die.
Other features and advantages of the present invention will become apparent from reading of the description hereinafter, with reference to the annexed drawings.